In a CDMA (Code Division Multiple Access) network, a system identifier (SID) identifies a service provider as well as a given geographical area. Networks within a system are given a network identifier or NID. A network is uniquely identified by the pair (SID, NID). FIG. 1 illustrates a network cloud 100 showing the relationship between various system identifiers and network identifiers.
A CDMA mobile device is typically pre-programmed by operators with an entity called a Preferred Roaming List (PRL). A PRL can also be downloaded to the mobile device using known over the air provisioning methods. FIG. 2 illustrates a simplified representation of a conventional preferred roaming list 102. The PRL, which comprises of a number of records, indicates which systems the mobile device is allowed to acquire. In this example, each record identifies a system by its (SID, NID) pair and provides the frequencies that the mobile device is to use when attempting to acquire the system. For each record, there can be an indicator of whether the system is preferred, the roaming status, the relative priority of the system, and its geographic region. As part of system acquisition, the mobile device searches for a CDMA Pilot Channel on a set of frequencies based on the PRL. The (SID/NID) information of the acquired system is conveyed to the mobile device on a Sync Channel once the mobile device has acquired the Pilot Channel. The PRL only contains the information about which systems the mobile device is allowed to acquire. It does not have any information about the type of services that are allowed on a given network. Typically, it only indicates that a certain degree of voice service is available on a network.
An “always-on always connected” mobile device needs to maintain data connectivity all the time to support seamless mobility. This requires the mobile device to re-establish its data connectivity whenever it changes systems. However, the mobile device has no a priori knowledge as to whether it is allowed to make a data call on a given system. Even if the network indicates that it is capable of supporting packet data services, there is no guarantee that the mobile device will be allowed to make any data calls. The mobile device can only find out about such information after it makes a data call origination attempt. A mobile device can only have true data mobility if a data roaming services agreement exists between the relevant service providers. A roaming agreement between operators does not necessarily cover all available services. For example, two operators may have a voice services roaming agreement, but no packet data services roaming agreement. Currently, there is no standardized mechanism to convey this information to the mobile device. As a result, the mobile device is forced to make blind data call origination attempts to find out whether it is allowed to make data calls or not. This has a significant impact on the battery life, especially in a geographical area where the mobile device goes in and out of a system where data calls are not allowed. Therefore, there is a need for a device capable of efficiently handling interactions with a network with respect to data service availability.